This invention relates to novel transient antifoam compositions.
Silicone antifoams prepared from an inorganic filler, e.g. silica and a variety of organosiloxane polymers are well known in the art. However, many of such types of antifoams are generally hydrolytically stable in aqueous media with the exception of very acid or basic media. The good stability of such antifoams can be a detriment in a variety of applications. For example, since many of such compositions are not biodegradable, they can contribute to undesired stream pollution. Further, such materials may cause problems in certain applications due to an undesirable buildup of silicone oil such as fabric spotting in textile dyeing and in the coating of hydrocarbon analyzers used in waste water treatment plants. Moreover, good hydrolytic stability of an antifoam can be a detriment where short term foaming control is desired such as in the processing and packaging of foamy liquids such as shampoos, liquid cleaners, and the like. Thus, there is a clear need for transient antifoams in the art which will control undesirable foaming during the processing and packaging of liquids but which will not adversely affect the foaming properties of the liquids that are desired upon the use of said liquids.
It has now been discovered that antifoam compositions based on condensation products of partially hydrolyzed trifunctionalsilanes can be prepared which possess the property of transience, i.e. hydrolytic instability in aqueous foaming media.
Therefore, it is an object of this invention to provide novel antifoam compositions that are transient in aqueous foaming media. Other objects and advantages of this invention will become readily apparent from the following description and appended claims.
More particularly this invention is directed to a transient non-aqueous antifoam composition, said composition consisting essentially of the product resulting from heating, in the absence of water, a mixture consisting essentially of a finely divided silica filler and a condensation product of a partially hydrolyzed trifunctional silane, said condensation product having a residual alkoxy content of at least about 9 percent by weight, said silane being selected from the group consisting of RSiX.sub.3 and RSi(OR').sub.3 wherein R and R' are alkyl radicals and X is a halogen atom, and wherein the amount ratio of said silica filler to said condensation product ranges from about 1 to about 33 parts by weight of the silica filler per 100 parts by weight of the condensation product.